Three-dimensional metallic microstructures find applications as stents in medicine, as ultrabroadband antennas in communications, in micromechanical parts, or as structures of more fundamental interest in photonics like metamaterials. Direct metal printing of such structures using three-dimensional (3D) laser lithography is a promising approach, which enables the fabrication of 3D structures with sub-micron-sized features. Yet, this fabrication technique is not extensively applied, as fabrication speed, surface quality, and stability of the resulting structures are limited so far. To identify the limiting factors, we investigate the influence of light−particle interactions and varying scanning speed on heat generation and particle deposition in direct laser writing of silver. We introduce a theoretical model which captures diffusion of particles and heat as well as the fluid dynamics of the photoresist. Chemical reactions are excluded from the model, but particle production is calibrated using experimental data. We find that optical forces generally surmount those due to convection of the photoresist. Simulations predict overheating of the photoresist at laser powers similar to those found in experiments. The thermal sensitivity of the system is essentially determined by the largest particles present in the laser focus. Our results suggest that to improve nanoparticle deposition and to achieve higher writing speeds in metal direct laser writing, strong optical trapping of the emerging particles is desirable. Furthermore, precise control of the particle size reduces the risk of spontaneous overheating.

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Consideration of technologies for the use of concentrated solar power (CSP) leads to the conclusion that there is substantially more energy in the sun’s heat than there is in its light. At present, solar-thermal energy conversion and storage systems using CSP have the shortcomings of the use of high pressures and potential problems with corrosion. In the development of new materials and designs, two of the key issues of consideration are the: (a) thermal properties of the materials and (b) heat transfer within the system. Most current technologies utilise convective heat transfer of liquids but there are none that use conductive heat transfer with solid-state systems. The present work introduces such a system in the form of highly dense and aligned self-assembled graphite, which can be heated in air, provided the hot face temperature is at a temperature sufficiently low to avoid the onset of oxidation. Modelling of a small domestic-scale system, which has no competition in the marketplace, consisting of: (a) 4 m diameter concentrator, (b) block of graphite weighing ~160 kg, and (c) electricity generation system demonstrates that, in only 90 min and at ≤420°C, sufficient heat can be stored to supply 25% more than is required for a typical 24 h, domestic, electricity usage cycle.